Engine-flywheel hybrid

ABSTRACT

An engine-flywheel hybrid in which the engine power is varied mainly by the frequency of power cycles, not by the power per power cycle. The flywheel absorbs the energy from the power cycles and delivers energy. The rotary stop start mechanism stops and starts a crankshaft efficiently with minimal energy loss. This is accomplished by varying the offset of a double crank four bar linkage. The invention allows an engine&#39;s flywheel to be quickly be brought up to speed in about a half of a revolution, followed by combustion, expansion, and stopped one revolution after starting. Further, utilizing offset, the engine crankshaft will turn faster than the input shaft when the piston is at top dead center, shortening the time of highest heat transfer, making the engine more efficient. Also, that when used as an auto engine, the part load efficiency would be near the maximum efficiency of the engine, nearly doubling the miles per gallon of the auto.

BACKGROUND TO THE INVENTION

This invention relates primarily to a mechanism whose input shaft can bedriven by a flywheel and which stops and starts an output shaft whichcan drive the crankshaft of an engine.

The invention is the result of seeking a mechanism which could quicklystop an engine's crankshaft and quickly start an engine's crankshaft,and do so with minimal energy losses.

The invention is an alternative to a big starter motor which can quicklystart an engine.

SUMMARY

The purpose of the invention is to stop and start an output shaftefficiently with minimal energy loss. The invention enables anengine-flywheel hybrid in which the power can be controlled by thefrequency of power cycles. Conventional engines control power at an rpmby throttling and/or the amount of fuel injected per power cycle.

Given a double crank four bar linkage and a constant angular rate on theinput shaft, as the offset between the crank shafts is increased, theangular rate of the output shaft will approach infinitely fast andinfinitely slow (stopped). For the purpose of the Invention, theinfinitely slow angular rate (stopped) is useful, but the infinitelyfast angular rate is not. To stop the output shaft, the offset isincreased as much as is needed to achieve the infinitely slow angularrate. Away from the output shaft stopped position, the offset isdecreased to avoid an extremely high output shaft angular rate.

An engine crankshaft connected to the output shaft can be stopped bydeclutching it from the output shaft when the output shaft is stopped.And to restart, a clutch can engage when the output shaft is once againstopped.

Objects and Advantages

A double crank four bar linkage with variable offset when positionedbetween the flywheel and output shaft has the advantage that the kineticenergy from slowing the output shaft to a stop is transferred into fileflywheel, and later, the flywheel kinetic energy is used to bring theoutput shaft back up to speed.

The intended application is to quickly stop and later, to quickly startan engine's crankshaft. The engine crankshaft would be run a revolutionor two as often as is needed to provide the desired level of power. Inthis application, the advantages are:

1) When the mechanism is used to drive the crankshaft of an engine, e.g.an engine that fires once per crankshaft revolution, or every otherrevolution, the combustion and expansion could be somewhat faster thanthe flywheel speed. The flywheel would normally be operated within afairly narrow speed range. The power per combustion can be relativelyconstant. The operating parameters can be optimized for efficiency andemissions per combustion. This includes spark ignition, diesel and HCCI(homogenous charge compression ignition) engines' operation. (Duringwarmup the power per combustion could be lower. For maximum power, thespeed of the engine could be higher.)

2) At low to moderate power levels, some friction and some pumpinglosses are avoided by eliminating some cycling of the piston andcrankshaft.

3) When used with an engine for a car, the efficiency in typical usageshould be close to the maximum efficiency of the engine. This is nearlytwice the efficiency of conventional car engines in typical usage. Thiswould nearly double the miles per gallon.

4) The output shaft must turn at a faster rate than the input shaft tomake up for the slowing to a stop during part of the revolution. Theoutput shaft turns one revolution per input shaft revolution. Bychoosing some of that faster rate to be near the engine's piston(s) topdead center and early expansion, the duration of combustion and earlyexpansion would be shortened, lessening the heat loss during that time.Heat energy not lost through heat transfer during combustion and earlyexpansion remains in the combustion gas as heat and can do workexpanding against the piston. This increases efficiency as compared toslower operating designs which lose more heat, (all else equal). Thisadvantage is gained without an increase in piston speed. However, thepeak piston speed is a little higher.

5) The crankshaft would be turning slower than the flywheel 180 degreesafter the piston top dead center. In a two cycle engine, this lengthensthe purge time, longer than it would be in a conventional two cycleengine, i.e. which has the flywheel directly coupled to the crankshaft.Accordingly, this would allow faster engine operation and/or reducedport sizes.

The engine-flywheel combination should be lighter, cheaper and moreefficient than an engine-electric hybrid that uses batteries for energystorage.

DRAWING FIGURES

-   1. Slowing the output shaft.-   2. Output shaft stopped.-   3. Accelerating the output shaft.-   4. No clutch stopped configuration.-   5. Speedup of output shaft.-   6. Dog clutch.-   7. Eccentric offset change mechanism.-   8. Output shaft speed variation.-   9. Engine-flywheel hybrid.-   10. Power cycles as needed.

LIST OF REFERENCE NUMERALS

-   12. input shaft-   14. input shaft crankarm-   16. input shaft crankpin-   18. coupler-   20. output shaft crankpin-   22. output shaft crankarm-   24. output shaft-   26. output shaft stop tooth-   28. output shaft jaw-   30. rotary mechanism shaft-   32. deceleration dog (engaged position)-   34. deceleration dog (disengaged position)-   36. tooth on rotary mechanism shaft-   38. acceleration dog (disengaged position)-   40. acceleration dog (engaged position)-   42. rotary tooth-   44. rotary jaw-   50. pivot on input shaft support bracket-   52. input shaft support bracket-   54. input shaft-   56. eccentric on input shaft-   58. tooth for minimum offset-   60. jaw for minimum and maximum offset-   62. tooth for maximum offset-   64. jaw for cyclic offset-   66. tooth for cyclic offset-   68. link to cyclic hold bracket-   70. cyclic hold bracket-   72. pivot for cyclic hold bracket

DESCRIPTION Definitions

A crank's radius is the distance from the crankshaft axis to thecrankpin axis.A coupler connects the crankpins of a double crank four bar linkage.The offset is the distance between the shafts of a double crank four barlinkage.

Consider a double crank four bar linkage with the same dimension on theinput shaft crank radii and the coupler length. The input shaft wouldhave a constant angular rate. As the offset between the crank shafts isincreased, the angular rate of the output shaft will become infinitelyfast and infinitely slow (stopped), once per input shaft revolution. Forthe purpose of the invention, the infinitely slow angular rate (stopped)is useful, but the finitely fast angular rate is not.

Away from the vicinity of the stopped position, the offset is lessenedto avoid an extremely high output shaft angular rate.

With some offset, there will be an output shaft angle where the outputshaft axis, the input shaft axis and the input shaft crankpin axis lineup. The input shaft angle where the output shaft is stopped canreasonably be about 45 degrees past the lined up angle. Regarding theforce needed to stop the output shaft and anything connected to theoutput shaft, the force is transmitted through the output shaft crank,through the coupler to the input shaft crank. For less than about 30degrees, the forces on the bearings would be unduly multiplied by thelinkage involved. FIG. 1 shows the double crank four bar linkage slowingthe output shaft.

FIG. 2 shows the output shaft stopped. The inward movement of the offsetshaft tends to backup the output shaft. The turning of the input shafttends to pull the output shaft forward. When these two cancel each otherout, the output shaft is stopped.

FIG. 3 shows the output shaft being accelerated.

FIG. 7 shows an eccentric 56 on the input shaft which moves the inputshaft 12 cyclically between the offset needed for stopping the outputshaft and a lesser or no offset needed to achieve the desired speedthrough the maximum speedup. The input shaft 54 is mounted on a bracket52 which is mounted on a pivot 50. The phase of the eccentric 56 needsto be such that the maximum offset occurs near the stopping point of theoutput shaft 24. FIG. 7 eccentric offset change mechanism provides threemodes of operation, cycle between the minimum and maximum offset, stayat the minimum offset and stay at the maximum offset. The latter is onlyused by the FIG. 4 no clutch stopped configuration.

Different means could be used to change the offset. Cams are another wayto vary the offset, including desmodromic cams which provide positivemovement in both directions. Also, an actuator of some kind could varythe offset, e.g. a hydraulic cylinder.

When the offset is varied substantially harmonically, the offset neededfor the output shaft to come to a stop is slightly less then the couplerlength. The motion of the input shaft due to the decreasing offset plusthe motion of the input shaft crankpin due to the input shaft rotationtogether produce the crankpin motion. When the instantaneous center ofthis crankpin motion is lined up with the coupler endpoints, thecrankpin motion does not move the output shaft crankpin, i.e. the outputshaft is stopped. Call this the output shaft stopped angle.

FIG. 9 shows a way a second double crank four bar mechanism used toconnect the input shaft to a flywheel. The crank radii on the seconddouble crank could be longer so that angular rates, flywheel to inputshaft, wouldn't vary much due to the second double crank. This designwould allow both the output shaft axle and the flywheel axle to not moverelative to each other. The input shaft axle would move relative to bothof the preceding. By having the crank arms on both ends of the inputshaft phased the same, the side forces coupled into the input shaftbearings tend to be minimize i.e. the forces that would tend to move theinput shaft support bracket 52 about it's pivot. However, the twistingforces would remain.

A rotary mechanism connected to the output shaft, e.g. an engine'scrankshaft, can be stopped by declutching it from the output shaft whenthe output shaft is stopped. And to restart, a clutch can engage whenthe output shaft is once again stopped.

FIG. 6 shows a way to implement the clutch such that the clutch functionis implemented by an acceleration dog 40 which can accelerate the rotarymechanism and a deceleration dog 32 which can decelerate the rotarymechanism. When both dogs are engaged, the output shaft is firmlycoupled to the rotary mechanism.

With this clutch, the timing of clutch dogs engagement/disengagement isnot critical. The movement of the dogs into the engaged position canoccur over tens of degrees prior to engagement and similarly fordisengagement. There should be minimal shock loading on the dogs becausethe shaft speeds are matched, albeit briefly.

The engagement disengagement of dogs could be by a cam that is movedinto position which then engages/disengages the dogs as the input shaftreaches the cam profile that causes engagement/disengagement of thedogs.

With the output shaft clutched into an engine's crankshaft, the minimumoffset could be chosen to optimize the angular rate over time. FIG. 5shows the speedup of the output shaft 24. Also, with the phase betweenthe engine crankshaft and the output shaft such that there is asignificant speedup near the engine's piston(s) top dead center andearly expansion, the time of highest heat transfer is shortened. Thisincreases the efficiency of the engine. The rotary mechanism, e.g.engine crankshaft, would always be stopped at the same angle, includingat mechanism rest, e.g. engine shutdown. This is needed so that thepreceding dog clutches take up smoothly and the phase relationship ismaintained.

For a four cycle single cylinder engine, the offset could be varied overtwo crankshaft revolutions, e.g. by using a 1:2 gear reduction to drivean eccentric or a cam.

Operation

FIG. 7 shows the jaw for cyclic offset 64 engaged. The offset is variedsubstantially harmonically. The rotation of the eccentric on the inputshaft 56 causes the input shaft support bracket to oscillate 52. Withthis design, the offset needed for the output shaft to come to a stop isslightly less then the coupler length. The motion of the input shaft dueto the decreasing offset plus the motion of the input shaft crankpin dueto the input shaft rotation together produce the crankpin motion. Whenthe instantaneous center of this crankpin motion is lined up with thecoupler endpoints, the motion does not move the output shaft crankpin,i.e. the output shaft is stopped. Call this the output shaft stoppedangle. See FIG. 2.

Away from the vicinity of the stopped position, the substantiallyharmonic drive lessens the offset to avoid an extremely high outputshaft angular rate.

FIG. 8 shows a plot of output shaft speed variation for the offset fixedat the minimum offset and for the offset varying harmonically betweenthe maximum, 96.5% of the coupler length (also, the crank radii) and theminimum 33.3% of the coupler length.

A rotary mechanism connected to the output shaft, e.g. an engine'scrankshaft, can be stopped by declutching it from the output shaft whenthe output shaft is stopped. And to restart, a clutch can engage whenthe output shaft is once again stopped.

To stop the rotary mechanism 30, when the output shaft 24 is beingslowed to a stop by the deceleration dog 32, the acceleration dog 34 isdisengaged prior to the output shaft 24 stopping. During the slowing,the acceleration dog 34 will not be transmitting any force and would beeasy to disengage. Then after the rotary mechanism 30 is stopped, thedeceleration dog 32 is disengaged. This leaves the output rotarymechanism stopped. At this point, the rotary mechanism would beprevented from angularly drifting by a rotary 44 hold jaw engaged torotary tooth 44. Note that the preceding jaw and tooth are between thedog clutch and the rotary mechanism, out of the way of the dog clutch.

To restart, the acceleration dog 40 is engaged prior to when the outputshaft 24 stops. The acceleration dog makes contact at the output shaftstopped angle. Then as the output shaft is accelerated out of thestopped position by the acceleration dog, the rotary mechanism is alsoaccelerated. The deceleration dog 32 is engaged as the rotary mechanismis accelerated. With both dogs now engaged, the output shaft is firmlycoupled to the rotary mechanism.

Higher Speed Operation

For faster engine operation, the input shaft could be held at theminimum offset by the FIG. 7 offset change mechanism. This would beuseful when it was desired to operate the engine faster for more power.To transition to holding the input shaft at the minimum offset, when theinput shaft is at the minimum offset, disengage the jaw for cyclicoffset 64 and engage the jaw for minimum and maximum offset 62. Totransition back to cyclic offset variation, wait until the jaw forcyclic offset and the tooth for cyclic offset lineup, and then disengagethe jaw for minimum and maximum offset 62 and engage the cyclic dog 64.

In both the minimum and maximum offset hold positions, the input shaftsupport bracket 52 is held steady while the link 68 moves the cyclichold bracket 70 back and forth.

Starting the Engine

To start the engine, a starter motor could speed up the flywheelconnected to the input shaft. When the flywheel has enough energy tocycle the engine, the clutch is engaged and the engine is started andruns until the flywheel is turning faster. This allows a less powerfulstarter motor.

Engine Flywheel Hybrid Operation

For an engine-flywheel hybrid, the predicted flywheel speed a revolutionor two ahead would be estimated. The engine crankshaft would be stoppeduntil the predicted flywheel speed slowed to below a threshold, and thenthe engine would be started by engaging the clutch at the nextopportunity. Then the engine would run until the predicted flywheelspeed is faster than a second higher threshold, and then stop. Thiskeeps the flywheel in a fairly narrow speed range. This is somewhatsimilar to the hit and miss engines of about a century ago. FIG. 10shows the power cycles as needed behavior.

For more power than the preceding would provide, the higher speedoperation mode could be used.

For alternate firing of cylinders in a four cycle two cylinder engine,one cylinder would be part way into it's exhaust stroke and the othercylinder would be part way into it's compression stroke. This is for adouble crank where the input shaft crank angle is ahead of the outputshaft crank angle.

Note that when combustion and expansion occurs, the power flows out ofthe crankshaft, through the double crank to the input shaft, perhapsthrough a second double crank, to the flywheel.

DESCRIPTION AND OPERATION Alternative Embodiments

In this alternative embodiment, the coupler length, the input shaftcrank radius and output shaft crank radius have same dimension.

To stop the output shaft and keep it stopped, the offset would reachcoupler length at around 45 degrees after the output shaft, the inputshaft and the input shaft crankpin are all lined up, in that order.

Then the input shaft crankpin will spin the coupler around thestationary output shaft crankpin. In this output shaft stoppedconfiguration, an output shaftjaw 28 engaged to output shaft stop tooth26 would keep it from drifting angularly. Also, the offset must be heldsteady. FIG. 7 shows the eccentric offset change mechanism. To hold theoffset steady, engage the jaw for minimum and maximum offset 62 with thetooth for maximum offset 62 while disengaging the cyclic dog 64. Notethat no clutch is needed to stop the output shaft.

To transition out of the output shaft stopped configuration, the offsetis decreased, beginning at the input shaft angle when maximum offsetoccurs. This is also when the jaw for cyclic offset 64 and the tooth forcyclic offset 66 lineup, and then disengage the jaw for minimum andmaximum offset 62 and engage the cyclic dog 64.

Higher speed operation would be as in the first version.

Alternative to the dogs clutches of FIG. 6 is to use a right hand oneway jaw clutch plus a left band one way jaw clutch, one concentric tothe other. The engagement/disengagement could function similarly to thedog clutch.

CONCLUSION, RAMIFICATIONS AND SCOPE

Applicant submits that the rotary start stop mechanism can be used tomake an engine-flywheel hybrid which would be more efficient, lighterand cheaper than an engine-electric hybrid that uses batteries forenergy storage. Further, that when used as an auto engine, the part loadefficiency would be near the maximum efficiency of the engine, nearlydoubling the miles per gallon of the auto.

Many modifications and variations of the present invention are possiblein light of the above teachings. It is therefore to be understood thatwithin the scope of the appended claims, the invention may be practisedotherwise than specifically described.

1-6. (canceled)
 7. a mechanism driven by an input shaft which stops theoutput shaft once per revolution comprising: a. a double crank four barlinkage, with similar crank radii and coupler length, b. means toincrease the offset of the shafts of said four bar linkage to where theoutput shaft crankpin is close to the input shaft axis, sufficient tosubstantially stop the output shaft, c. means to decrease the offset ofthe shafts of said four bar linkage when the said output shaft crankpinis away from the input shaft axis, whereby the output shaft can bestopped once per revolution,
 8. The mechanism of claim 7 wherein thesaid means to increase the offset and said means to decrease the offsetcomprises: a. an input shaft support bracket mounted on a pivot b. saidinput shaft support bracket having a first tooth for holding at theminimum offset and a second tooth for holding at the maximum offset, c.an eccentric on said input shaft phased to have maximum offset when thesaid output shaft crankpin and the said input shaft are coincident, d. acyclic hold bracket mounted on a pivot, e. said cyclic hold brackethaving a third tooth for cyclic offset, f. a link connected from saideccentric to said cyclic hold bracket, g. a first jaw which may beengaged to said third tooth on said cyclic hold bracket to change thesaid input shaft offset cyclically, h. a second jaw which may be engagedto the said second tooth to hold at the maximum offset, i. said secondjaw which may be engaged to the said first tooth to hold at the minimumoffset, whereby the input shaft offset can be changed efficientlybetween minimum and maximum offset or held at the maximum offset or theminimum offset and the changeover between a fixed offset and a cyclicoffset may be accomplished when the offset is at an extreme.
 9. Themechanism of claim 7 further including a mechanism to selectively startand stop an attached mechanism comprising the method of: a. engage theacceleration dog prior to the said output shaft stopping, b. after thesaid output shaft starts, engage a deceleration dog, c. to stop the saidattached mechanism, d. disengage the acceleration dog prior to the saidoutput shaft stopping, e. after the said output shaft stops, disengagesaid deceleration dog,